Fuel efficiency is a significant element of the overall economics of a road transportation vehicle, e.g., semi-truck (“tractor”) with a trailer. Fuel efficiency of the road vehicles is mostly determined by engine efficiency, rolling resistance of the wheels, stop-and-go traffic (i.e., acceleration and deceleration), drag coefficient, and trailer loading. At relatively high and steady velocity, typically referred to as “highway driving,” the air flow drag often dominates energy losses of the vehicle. Conversely, at lower speeds or at idle, high temperature in the engine compartment may reduce engine efficiency, and may also increase harmful emissions.
Some conventional technologies attempt to improve the cooling of the engine compartment by installing ducts on the sides of the engine hood for better venting of the engine compartment. FIG. 1A is an example of the conventional technology for the engine compartment venting. The illustrated engine compartment panel 15 has several ducts 1 with side vents 6 that allow hot air to escape from the engine compartment.
FIG. 1B shows a detail of the side vent 6 from FIG. 1A. In operation, when pressure inside the engine compartment exceeds certain predetermined value, a flap 8 bends to allow hot air from the interior of the engine compartment to escape through the side vent 6. In general, higher pressure within the engine compartment bends the flap 8 more, allowing for faster venting of the hot air. When the pressure inside the engine compartment falls below certain design value, the flap 8 bends back to its original position to close the vent 6.
However, the operation of the conventional ducts generally does not relate to the speed of the vehicle or the temperature under the hood, therefore resulting in under-venting or over-venting in comparison to the needed amount of venting and cooling of the engine compartment. Furthermore, with the conventional technology illustrated in FIGS. 1A and 1B, the venting ducts protrude into the engine compartment—generally an already crowded space that is mostly occupied by the engine and the auxiliary systems.
Accordingly, there remains a need for cost- and space-effective venting of the engine compartment that also improves the aerodynamics of the vehicle.